Monopole antenna array source for semiconductor process equipment

ABSTRACT

A plasma reactor includes a chamber body having an interior space that provides a plasma chamber, a gas distribution port to deliver a processing gas to the plasma chamber, a workpiece support to hold a workpiece, an antenna array comprising a plurality of monopole antennas extending partially into the plasma chamber, and an AC power source to supply a first AC power to the plurality of monopole antennas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Application Ser. No.62/511,885, filed on May 26, 2017, the entire disclosure of which isincorporated by reference.

TECHNICAL FIELD

This specification relates to wafer processing systems and relatedmethods.

BACKGROUND

Processing of a workpiece such as a semiconductor wafer can be carriedout using a form of electromagnetic energy, such as RF power ormicrowave power, for example. The power may be employed, for example, togenerate a plasma, for carrying out a plasma-based process such asplasma enhanced chemical vapor deposition (PECVD) or plasma enhancedreactive ion etching (PERIE). Some processes need extremely high plasmaion densities with extremely low plasma ion energies. This is true forprocesses such as deposition of diamond-like carbon (DLC) films, wherethe time required to deposit some type of DLC films can be on the orderof hours, depending upon the desired thickness and upon the plasma iondensity. A higher plasma density requires higher source power andgenerally translates to a shorter deposition time.

A microwave source typically produces a very high plasma ion densitywhile producing a plasma ion energy that is less than that of othersources (e.g., an inductively coupled RF plasma source or a capacitivelycoupled RF plasma source). For this reason, a microwave source would beideal. However, a microwave source cannot meet the stringent uniformityrequired for distribution across the workpiece of deposition rate oretch rate. The minimum uniformity may correspond to a process ratevariation across a 300 mm diameter workpiece of less than 1%.

SUMMARY

In one aspect, a plasma reactor includes a chamber body having aninterior space that provides a plasma chamber, a gas distribution portto deliver a processing gas to the plasma chamber, a workpiece supportto hold a workpiece, an antenna array comprising a plurality of monopoleantennas extending partially into the plasma chamber, and an AC powersource to supply a first AC power to the plurality of monopole antennas.

Implementations may include one or more of the following features.

The workpiece support may be configured to hold the workpiece such thata front surface of the workpiece faces the antenna array. The pluralityof monopole antennas may extend in parallel into the plasma chamber. Aportion of each monopole antenna that extends into the plasma chambermay be cylindrical. A portion of each monopole antenna that extends intothe plasma chamber may be conical.

The plurality of monopole antennas may extend through a plate portion ofthe chamber body. The plate portion may provide a ceiling of the plasmachamber. Each monopole antenna may include an outwardly extending flangepositioned on a far side of the plate portion from the plasma chamber.The plate portion may be conductive. Each sheath of a plurality ofinsulative sheaths may surround a portion of a monopole antenna thatextends through the plate portion to insulate the monopole antenna fromthe plate portion. Each monopole antenna may have an outwardly extendingflange positioned on a far side of the plate portion from the plasmachamber, and each insulative sheath may have an outwardly extendingflange separating the flange of the monopole antenna from the plateportion.

The workpiece support may be configured to hold the workpiece such thata front surface of the workpiece is perpendicular to a long axis of theplurality of monopole antennas. The workpiece support may be configuredto hold the workpiece such that a front surface of the workpiece facesthe antenna array. The plurality of monopole antennas face the workpiecesupport without an intervening barrier.

There may be plurality of microwave or RF transparent window sheaths,and each window sheath may surround a portion of a monopole antenna thatprojects into the plasma chamber. The plurality of window sheathcomprise a material selected from ceramic and quartz.

The monopole antennas may be spaced uniformly across the plate portion.The monopole antennas may have a uniform size and shape. The monopoleantennas may have non-uniform size or shape. The plurality of monopoleantennas may be arranged in a hexagonal pattern.

A first gas distribution plate may have a first plurality of gasinjection orifices, a first process gas plenum overlying first gasdistribution plate and a first process gas supply conduit coupled to thefirst process gas plenum. The plurality of monopole antennas may extendthrough the gas distribution plate. The plurality of gas injectionorifices may be positioned in spaces between the monopole antennas.

A second gas distribution plate may have a second plurality of gasinjection orifices that couple to a third plurality of gas injectionorifices in the first gas distribution plate, a second process gasplenum overlying the second gas distribution plate, and a second processgas supply conduit coupled to the second process gas plenum. Theplurality of monopole antennas may extend through the first gasdistribution plate and the second gas distribution plate.

The AC power source may be configured to apply microwave power to theplurality of monopole antennas. The AC power source is configured toapply microwave power to the plurality of monopole antennas so as togenerate plasma in the plasma chamber. The AC power supply may include aplurality of auto-tuners, each auto-tuner coupled to a differentmonopole antenna.

The AC power source may be configured to generate AC power on aplurality of power supply lines at a plurality of different phases, theplurality of monopole antennas may be divided into a plurality ofgroups, and different groups of monopole antennas may be coupled todifferent power supply lines. The number of different power supply linesmay be at least 4. Each group of monopole antennas may be defined by aspatially continuous zone of adjacent monopole antennas. Monopoleantennas in spatially adjacent zones may be coupled to power supplylines that provide AC power at sequentially adjacent phases. Theplurality of monopole antennas may be divided into N groups and the ACpower source is configured to generate AC power on N power supply linesphases separated by 360/N. N may be 4 or 6 or 8. The spatiallycontinuous zones may be a plurality of linear rows. The spatiallycontinuous zones may be a plurality of circular sectors.

In another aspect, a method of plasma processing a workpiece includessupporting a workpiece in a plasma chamber, delivering a processing gasto the plasma chamber, and generating a plasma in the chamber byapplying AC power to an antenna array that comprises a plurality ofmonopole antennas extending partially into the plasma chamber.

In another aspect, a plasma reactor includes a chamber body having aninterior space that provides a plasma chamber, a process gasdistribution system to deliver a processing gas to the plasma chamber, aworkpiece support to hold a workpiece, and an antenna array comprising aplurality of monopole antennas. The process gas distribution systemincludes a first gas distribution plate having a first plurality of gasinjection orifices, a first process gas plenum overlying gasdistribution plate, and a first process gas supply conduit coupled tothe first process gas plenum. The plurality of monopole antennas extendthrough the first gas distribution plate and partially into the plasmachamber.

Implementations may include one or more of the following features.

The plurality of gas injection orifices may be positioned in portions ofthe first gas distribution plate that separate the monopole antennas.The process gas distribution system may include a gas plenum platehaving a recess on a surface thereof that face the first gasdistribution plate, the recess providing the plenum. The plurality ofmonopole antennas may extend through the gas plenum plate. The pluralityof monopole antennas may extend through non-recessed regions of the gasplenum plate between the recesses. Each monopole antenna may besurrounded by a respective portion of the recess.

A second gas distribution plate may have a plurality of passages thatcouple to a second plurality of gas injection orifices in the first gasdistribution plate. A second process gas plenum overlying may overliethe second gas distribution plate, and a second process gas supplyconduit may be coupled to the second process gas plenum. The pluralityof monopole antennas may extend through the first gas distribution plateand the second gas distribution plate.

The plurality of monopole antennas may be arranged in a hexagonalpattern. The plurality of gas injection orifices may be arranged in ahexagonal pattern. The plurality of monopole antennas may extend inparallel into the plasma chamber. An AC power source may be configuredto apply microwave or RF power to the plurality of monopole antennas soas to generate plasma in the plasma chamber.

In another aspect, a plasma reactor includes a chamber body having aninterior space that provides a plasma chamber, a grid filter extendingacross the interior space and diving the plasma chamber into an upperchamber and a lower chamber, a gas distribution port to deliver aprocessing gas to the upper chamber, a workpiece support to hold aworkpiece in the lower chamber, an antenna array comprising a pluralityof monopole antennas extending partially into the upper chamber, and anAC power source to supply a first AC power to the plurality of monopoleantennas.

Implementations may include one or more of the following features.

The plurality of monopole antennas may extend in parallel into the upperchamber. The plurality of monopole antennas may extend perpendicular tothe grid filter. The workpiece support may be configured to hold theworkpiece parallel to the grid filter. The grid filter may be positionedbetween the plurality of monopole antennas and the workpiece support.The AC power source is configured to apply microwave power to theplurality of monopole antennas so as to generate plasma in the upperchamber.

A second process gas distribution system may deliver a second processinggas to the lower chamber. The grid filter may include a gas distributionplate having a first plurality of gas injection orifices and a gasplenum plate overlying the gas distribution plate. A recess in a bottomsurface of the gas plenum plate may provide a plenum for the secondprocessing gas to flow to the gas injection orifices. The grid filtermay have a plurality of apertures through the gas plenum plate and thegas distribution plate for flow of plasma or electrons from the upperchamber to the lower chamber.

In another aspect, a plasma reactor includes a chamber body having aninterior space that provides a plasma chamber, a gas distribution portto deliver a processing gas to the plasma chamber, a workpiece supportto hold a workpiece, an antenna array comprising a plurality of monopoleantennas extending partially into the plasma chamber, and an AC powersource to supply a first AC power to the plurality of monopole antennas.The plurality of monopole antennas are divided into a plurality ofgroups of monopole antennas, and the AC power source is configured togenerate AC power on a plurality of power supply lines at a plurality ofdifferent phases, and different groups of monopole antennas are coupledto different power supply lines.

Implementations may include one or more of the following features.

Each group of monopole antennas may be defined by a spatially continuouszone of adjacent monopole antennas. The monopole antennas in spatiallyadjacent zones are coupled to power supply lines that provide AC powerat sequentially adjacent phases. The spatially continuous zones may be aplurality of linear rows. The spatially continuous zones may be aplurality of sectors arranged angularly around a central axis.

The plurality of monopole antennas may be divided into N groups and theAC power source is configured to generate AC power on N power supplylines at phases separated by 360/N. The groups may form a plurality oflinear rows, and the linear rows may have equal width. The groups mayform a plurality of sectors arranged angularly around a central axis,and the plurality of sectors may subtend equal angles around the centralaxis. The plurality of sectors may be circular sectors or triangularsectors.

The AC power source may be configured to apply a common phase shift tothe phases on the N power supply lines. The AC power source may beconfigured to increase the phase shift linearly over time. The AC powersource may be configured such that a phase on a respective power supplyline has a phase shift frequency between 1-1000 Hz.

The AC power source is configured to apply microwave or RF power to theplurality of monopole antennas so as to generate plasma in the plasmachamber. The AC power supply comprises a plurality of auto-tuners, eachauto-tuner coupled to a different monopole antenna. The reactor mayinclude a supplemental monopole antenna. The supplemental monopoleantenna may be positioned at a center of the array. The center monopoleantenna may be driven with a one-phased signal.

In another aspect, a method of plasma processing a workpiece includessupporting a workpiece in a plasma chamber, delivering a processing gasto the plasma chamber, and generating a plasma in the chamber bygenerating AC power on a plurality of power supply lines at a pluralityof different phases, and applying the AC power at the plurality ofdifferent phases from the power supply lines to respective differentgroups of monopole antennas that extend partially into the plasmachamber.

Advantages of the foregoing may include, but are not limited to, thosedescribed below and herein elsewhere. A plasma reactor in accordance tocertain aspects can provide improved process uniformity, e.g., improveduniformity of deposition or etching of a layer of material onto asubstrate. The plasma reactor can use ions or radicles for processesmore effectively, thus can provide improved process speed, e.g.,deposition rate or etching rate, and thus increasing throughput. Theplasma reactor can have better temperature control thus provide a morestable process.

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description below. Other potential features, aspects,and advantages will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional side view of a plasma reactor inaccordance with a first embodiment.

FIG. 2 is a schematic bottom view of a ceiling of the plasma reactor ofFIG. 1.

FIG. 3 is schematic cross-sectional side view of a plasma chamber inaccordance with a second embodiment.

FIG. 4 is an enlarged view of a portion of FIG. 1.

FIG. 5 is an example of a different embodiment of the portion in FIG. 4.

FIG. 6 is a schematic top view of an antenna array in accordance with afirst embodiment.

FIG. 7 is a schematic top view of an antenna array in accordance with asecond embodiment.

FIG. 8 is a schematic top view of an antenna array in accordance with athird embodiment.

DETAILED DESCRIPTION

Processing of a workpiece, such as a semiconductor wafer, can be carriedout in a plasma reactor. Electromagnetic energy, such as RF power ormicrowave (MW) power, can be employed, for example, to generate a plasmain a chamber to carry out a plasma-based process, e.g., plasma enhancedchemical vapor deposition (PECVD) or plasma enhanced reactive ionetching (PERIE). Some processes, e.g., the deposition of diamond-likecarbon (DLC) films, need high plasma ion densities with low plasma ionenergies. A higher plasma density requires a higher source power andgenerally results in a shorter deposition time.

An advantage of a microwave source is that such a source can produce avery high plasma ion density while producing a plasma ion energy that isless than that of other sources (e.g., an inductively coupled RF plasmasource or a capacitively coupled RF plasma source). Another advantage ofa microwave plasma source is the capability to generate plasma in a widerange of chamber pressures, generally from above atmospheric pressuredown to 10⁻⁶ Torr or below. This enables microwave plasma processing tobe used across a very wide range of processing applications.

However, many microwave sources cannot meet the stringent uniformityrequirements of semiconductor processing. The minimum uniformity maycorrespond to a process rate variation across a 300 mm diameterworkpiece of less than 1%. In systems in which microwaves propagate intothe chamber through slots in a waveguide, the antenna can have aperiodic power deposition pattern reflecting the wave pattern of themicrowave emission and the slot layout, which rendering the process ratedistribution non-uniform. This prevents attainment of the desiredprocess rate uniformity across the workpiece. One technique to reducingthe uniformity problem is to use a rotary antenna in the plasma chamber.Unfortunately, this technique can have various setbacks, such asmicrowave leakage through the timing belt slots of antenna rotation, andmicrowave auto-tuning difficulty due to the antenna rotation. Inaddition, gas distribution from the center to edge of a substrate mightnot be uniform.

However, the microwave power can be delivered into the chamber through amonopole antenna array. Microwaves propagate into the chamber throughthe antennas. This can mitigate the problem of slots in an antennagenerating a periodic power deposition pattern. In addition, significantimprovements in uniformity can result from, for example, applying powerto groups of antennas at different phases, thus mimicking a rotarysource.

Another limitation to the processing rate is the amount of microwavepower that can be delivered to a process chamber without damaging oroverheating the gas plate or the grid filter. A conventional gas plateprovides a vacuum boundary of the chamber and consequently can besubject to significant mechanical stress, rendering the gas platevulnerable to damage from overheating. Such a gas plate can withstandonly low microwave power levels. As a result, some processes, e.g., DLCdeposition processes, can require hours to reach a desired DLC filmthickness. This problem can be addressed by providing a window sheathsurrounding each monopole antenna that projects into the plasma chamber,the danger of mechanical stress is reduced and the power that can beapplied can be increased.

Referring to FIG. 1, a plasma reactor 10 includes a chamber body 101that has a side wall 102, e.g., of cylindrical shape, to enclose achamber 100. The sidewall 102 is formed of a material that is opaque tomicrowaves in order to confine microwaves within the chamber. Thesidewalls can be a conductive material, e.g., a metal.

The chamber 100 can be divided by a grid filter 112 into an upperchamber 100 a and a lower chamber 100 b. The lower chamber 100 b is adrift space because of a lack of substantial electric field therein inthe absence of an applied bias voltage. The sidewall 102 can include anupper sidewall 102 a that surrounds the upper chamber 100 a and a lowersidewall 102 b that surrounds the lower chamber 100 b.

A ceiling 104, that can be formed of a conductive material, overlies theupper chamber 100 a. The ceiling 104 can be provided by a showerhead118.

The reactor 10 further includes an array 108 of monopole antennas 116connected to a AC power source 110 that is configured to generate powerat a microwave or RF frequency. The monopole antenna array 108 includesa plurality of monopole antennas 116 that extend partially into theupper chamber 100 a. The antennas 116 are formed of a conductivematerial, e.g., copper or aluminum, or another metal coated with highconductive layer. In some implementations, the antennas 116 project inparallel into the upper chamber 100 a. The antennas 116 can projectthrough the ceiling 104 of the chamber body 101. A bottom surface ofeach antenna 116 can face the grid filter 112.

In some implementations, the bottom surfaces of the antennas 116 arecoplanar, e.g., the antennas 116 project by the same amount into thechamber 100. Alternatively, the bottom surfaces of some antennas 116,e.g., antennas in the center of the array 108, can be recessed relativeto other antennas. In this case, the antennas 116 at the edge of thearray 108 project further into the chamber 100 than the antennas 116 atthe center of the array 108.

The antenna array 108 can be split into groups of antennas, e.g., groupswith equal amount of antennas. This permits different power to beprovided at different phases to different groups of antennas 116 withinthe antenna array 108.

In one example, the perimeter of the antenna array 108 forms a hexagonalconfiguration (see FIG. 6). This permits the array to be divided intosix triangular groups with equal amount of antennas each (see FIG. 7).The perimeter can also be configured in other shapes, e.g., square,pentagonal, heptagonal, or octagonal. These shapes can also be dividedinto groups that each cover a triangular section of the shape, e.g.,four, five, seven, or eight groups.

The antennas can be disposed with substantially uniform spacing in thearray 108. Within the array 108, the antennas can be disposed in ahexagonal or rectangular pattern (see FIG. 2). The pitch of the antennasin the array can be about ½ to 2 inches. The antennas 116 can have beuniformly sized and shaped in their cross-section, e.g., the antennascan have a circular cross-section. Alternatively, some of the antennascan have different cross-sectional sizes, e.g., antennas at the centercan have a larger diameter. The length L of the portion 116 c of theantenna 116 that projects into the chamber can be greater than the widthW (see FIG. 4).

In some implementations, the antennas project through a showerhead 118,e.g., a dual channel showerhead (DCSH). The showerhead 118 can include agas distribution plate 120 and a gas plenum plate 122. A long axis ofthe antennas 116 can be perpendicular to a lower face of the showerhead118.

A workpiece support pedestal 106 for supporting a workpiece 124 in thelower chamber 100 b has a workpiece support surface 106 a. The workpiecesupport pedestal 106 can be moveable, e.g., by a linear actuator, alongan axial direction, e.g., to adjust the height of the workpiece supportpedestal in the chamber 100. The workpiece support surface 106 a canface the grid filter 112. A long axis of the antennas 116 can beperpendicular to the support surface 106 a of the support pedestal 106.

In some implementations, the pedestal 106 includes one or more heatingelements 107 configured to apply heat to the workpiece 124. The heatfrom the heating elements 107 can be sufficient to anneal the workpiece124 when the workpiece is supported on the pedestal 106 and theprecursor gas (if used) has been introduced into the chamber 100 b. Theheating elements 107 may be resistive heating elements. With the heatingelements 107 positioned, e.g., embedded in, the pedestal 106, theworkpiece 124 is heated through contact with the pedestal. An example ofa heating element 107 includes a discrete heating coil. Electrical wiresconnect an electrical source (not shown), such as a voltage source, tothe heating element, and can connect the one or more heating elements107 to a controller.

The pedestal 106 can be configured to hold the workpiece 124 such that afront surface of the workpiece 124 a faces the grid filter 112; thefront surface 124 a can be parallel to the grid filter 112. In anotherexample, as discussed in further detail below, the pedestal 106 can beconfigured so that the front surface of the workpiece 124 a faces theantenna array.

In some implementations, the pedestal 106 can mechanically rotate aboutan axis of rotation that coincides with an axis of symmetry 106 b of thepedestal. This rotation can improve the plasma uniformity of the processon the workpiece 124. The pedestal 106 can be rotated by a rotationmotor (not shown) attached to the pedestal.

The AC power source 110 is connected to the monopole antennas 116. Forexample, the power source 110 can be coupled to the antennas array 108via one or more coaxial cables. The power source 110 can operate afrequency range of 30 Hz to 30 GHz. For example, the power source 110can generate power at microwave frequencies, e.g., 300 MHz to 30 GHz, atRF frequencies, e.g., 300 kHz to 30 MHz, and/or at VHF frequencies,e.g., 30 MHz to 300 MHz. The power source 110 is configured orcontrolled to apply microwave or RF power to the plurality of monopoleantennas so as to generate plasma in the chamber 100. In someimplementations, the power source 110 can also apply a DC voltage.

As will be described further below, the AC power source 110 can beconfigured to generate AC power on a plurality of power supply lines atdifferent phases, and supply power through those lines to differentgroups of the monopole antennas 116.

In some implementations, a conductive shield 134 that includes acylindrical side wall 136 surrounds the upper sidewall 102 a and extendsover the ceiling 104 (e.g., over the showerhead 118). The conductiveshield 134 can be electrically grounded.

In some implementations, an upper gas injector assembly provides processgas into the upper chamber 100 a. In some implementations, the upper gasinjector assembly can include a plurality of upper gas injectors 138,e.g., to provide gas from the ceiling 104 of the chamber 100. The gasinjectors 138 allow uniform gas injection into the plasma chamber 100 a.

For example, gas is supplied from a gas supply 126 through a gas conduit130 to one or more gas distribution ports 128. The gas distributionport(s) 128 can be coupled to a gas plenum. For example, a recess 122 ain the underside of the gas plenum plate 122 can provide the plenum forthe flow of gas from the conduit 130. The gas plenum plate 122 overliesa gas distribution plate 120. The gas distribution plate 120 has aplurality of gas injection orifices 120 a that extend through the gasdistribution plate 120 and that are fluidically coupled to the gasplenum to distribute the gas into the upper chamber 100 a. The orifices120 a and optionally a portion of the recess 122 a can provide the uppergas injectors 138.

The gas injection orifices are positioned in spaces between the monopoleantennas 116. For example, referring to FIG. 2, if the monopole antennas116 are arranged in a hexagonal array, the gas injection orifices 120 acan similarly be arranged in a hexagonal array, e.g., with each monopoleantenna 116 surrounded by six orifices 120 a. Similarly, the recess 122a in the bottom surface of the gas plenum plate 122 can be ahoneycomb-shaped, with the antenna 116 extending through thenon-recessed portion, i.e., the center of each cell of the honeycomb.

Although FIG. 1 illustrates the plenum as being formed by a recess inthe bottom of a plenum plate, a volume 146 above the array 108 ofmonopole antennas 116 could provide a plenum for gas supply. In thiscase, for some implementations, the plenum plate 122 is omitted, andpassages extend entirely through the showerhead 118 (which iseffectively the gas distribution plate 120) to connect directly to thevolume 146. This volume would be enclosed by the cover 134, and gaswould be supplied by a port extending through the cover 134.Alternatively, the plenum plate 122 can serve as a second gasdistribution plate that both the recess for the plenum, and a pluralityof passages that couple to another plurality of gas injection orificesin the first gas distribution plate 120. In this case, the volume 146can provide a second process gas plenum overlying the second gasdistribution plate 122, and a second process gas supply conduit coupledto the second process gas plenum. This permits two different processgases to be supplied to the chamber. The monopole antennas 116 extendthrough both the first gas distribution plate 120 and the second gasdistribution plate 122.

Returning to FIG. 1, although a showerhead 118 in the ceiling of thechamber is illustrated, alternatively or in addition, gas could also besupplied through the side walls, e.g., through apertures in the uppersidewall 102 a.

In some implementations, a lower gas injector assembly provides processgas into the lower chamber 100 b. The lower gas injector assembly caninclude a plurality of lower gas injectors 158, e.g., to provide gasfrom the ceiling 104 of the chamber 100. The gas injectors 158 allowuniform gas injection into the plasma chamber 100 a. The lower gasinjectors can be placed as part of, instead of, or below the grid filter112.

For example, the lower gas injector assembly could be similar to theupper gas injector assembly. In particular, the grid filter 112 caninclude a gas distribution plate 150 and a gas plenum plate 152. Arecess 152 a in the underside of the gas plenum plate 152 can providethe plenum for the flow of gas through a second distribution port 148from the conduit 130. The gas distribution plate 150 has a plurality ofgas injection orifices 150 a that extend through the gas distributionplate 120 and that are fluidically coupled to the gas plenum todistribute the gas into the lower chamber 100 b.

Again, although gas injection orifices 150 a in the grid filter 112 areillustrated, alternatively or in addition, gas could also be suppliedthrough the side walls, e.g., through apertures in the lower sidewall102 b.

In such implementations, gas species and gas flow rates into the upperand lower chambers 100 a, 100 b are independently controllable. In oneexample, an inert gas is supplied into the upper chamber 100 a and aprocess gas is supplied into the lower chamber 100 b. The inert gas flowrates can be controlled to substantially prevent convention or diffusionof gases from the lower chamber 100 b into the upper chamber 100 a,providing substantial chemical isolation of the upper chamber 100 a. Thegas delivery system can include an exhaust system 140, e.g., including avacuum pump, to exhaust the precursor gas from the upper chamber 100 a,thereby depressurizing the chamber 100.

In some implementations, the AC power source 110 comprises a pluralityof auto-tuners, each auto-tuner coupled to a different monopole antenna116. The level of RF power from the RF generator 110 is highlycontrollable. This may allow the plasma density in the upper chamber 100a to be substantially controlled (enhanced) by the RF power from the RFpower generator. As a result, the formation of lattice defects or voidsin the deposited material can be reduced.

In some implementations, the grid filter 112 is a flat disk shape. Thegrid filter can extend across the chamber 100. The grid filter 112 isformed with an array of plural openings 112-1. The openings 112-1 can beuniformly spaced across the grid filter 112. The axial thickness T ofthe grid filter 112 and the diameter, d, of the plural openings 112-1can be selected to promote flow through the grid filter 112 of energeticdirected beam electrons while impeding flow of non-beam (low-energy)electrons and plasma ions through the grid filter 112.

The plasma in the lower chamber 100 b may have different characteristicsfrom the plasma in the upper chamber 100 a. The grid filter 112 mayfunction as a filter to substantially electrically isolate the upper andlower chambers 100 a, 100 b from one another. In some implementations,the grid filter 112 is formed of a conductive or semi-conductivematerial. For example, the grid filter 112 can be a metal, such asaluminum. The grid filter 112 can be connected to ground or can beelectrically floating. The grid filter 112 can be RF hot or groundeddepending on whether the substrate is grounded or RF hot. In someimplementations, the grid filter 112 is formed of a non-conductivematerial. In some implementations, the grid filter 112 is coated with aprocess compatible material such as silicon, carbon, silicon carboncompound or a silicon-oxide compound, or an oxide material, e.g., asaluminum oxide, yttrium oxide, or zirconium oxide.

Referring now to FIG. 3, a single-chamber plasma reactor 10 includes aplasma chamber 100 containing the workpiece support 106. In general,except as described below, the reactor of FIG. 3 would be the same asthe reactor of FIG. 1. For example, the plasma reactor can use the samearray of monopole antennas.

Unlike the implementation illustrated in FIG. 1, the plasma reactorillustrated in FIG. 3 is not divided into an upper chamber and a lowerchamber; there is no grid filter extending across the chamber. As such,the reactor has only the single chamber 100. So the array 108 ofmonopole antennas will generate the plasma in the same chamber as theworkpiece support. The chamber 100 is enclosed by a sidewall 102 formedof a microwave opaque material, such as a metal. In someimplementations, the sidewall 102 includes a transparent window or is atransparent material such as a dielectric material.

In this example, a gas injector assembly includes a plurality of gasinjectors 138 distribute gas directly into the plasma chamber 100 wherethe workpiece 124 is located. Gas is supplied from a gas supply 126through a gas conduit 130. One or more gas distribution ports 128 arecoupled to a gas plenum provided by a recess 122 a in an underside ofthe gas plenum plate 122. The gas plenum plate 122 overlies a gasdistribution plate 120. The gas distribution plate 120 has a pluralityof gas injection orifices 120 a which extend through the gasdistribution plate 120 and are fluidically coupled to the gas plenum.The orifices 120 a, optionally with a portion of the recess 122 a, canprovide the gas injectors 138 that distribute the gas into the chamber100. The gas injection orifices are positioned in spaces betweenmonopole antennas 116.

The AC power source 110 provides the MW frequency needed to an array ofmonopole antennas 108. The monopole antennas 116 extend parallel intothe plasma chamber 100. A potential advantage of this configuration isthat it can provide a high density plasma to processes that require highenergy such as DLC deposition, and can increase plasma efficiency andwafer temperature.

Referring now to FIG. 4, the dual channel showerhead 118 includes thegas plenum 122 and gas distribution plate 120. In one example, theshowerhead is made of, e.g., aluminum. In some implementations, theshowerhead includes a disk shaped plate with perforations on a bottomsurface that provide the orifices 120 a for dispensing reactant gasesuniformly over a second parallel planar surface, such as a grid filteror a workpiece. In some implementations, the orifices provide nozzleswith a narrow passage 120 b that leads from the plenum to a flarednozzle 120 c at the bottom surface of the showerhead 118.

In addition, the showerhead 118 includes orifices 118 a extending from atop surface to a bottom surface, each orifice sized to hold anindividual monopole antenna 116. The spacing between the orifices 118 acan be selected to effectively maximize the number of antennas 116 inthe showerhead 118 in consideration of the power and current. Forexample, the spacing between antennas 116 can be such that adjacentantennas 116 are close, e.g., less than 10 mm apart, but do not touch.The antennas 116 should not be so close that shorting may occur. Forexamples, the adjacent antennas 116 can be more than 2 mm apart.

As illustrated in FIG. 4, each monopole antenna 116 can have acylindrical shaft 116 a that projects into the chamber 100 a. However,monopole antennas of different shapes and lengths may be suitable fordifferent purposes and applications during the deposition or etchprocess. For example, as shown in FIG. 5, the portion 216 a of themonopole antennas that projects into the chamber 100 a can have aconical shape. Returning to FIG. 4, the antenna 116 can have anoutwardly projecting flange or shoulder 116 b. The flange or shoulder116 can be a circular projection that extends laterally from the shaft116 a. The flange or shoulder 116 is positioned above the showerhead118. The orifice 118 a allows the shoulder 116 b of the monopole antenna116 to sit on the top surface of the showerhead 118 while allowing theshaft 116 a to project beyond the showerhead 118 into the plasma chamber100. This can fix the vertical position of the bottom of the antenna 116within the chamber 100.

Monopole antennas 116 can reach elevated temperatures (e.g., 30° C. to400° C.), due to the high voltages applied during the process.Temperature control can be provided by a channel (not shown) in asupport for the antenna, e.g., a channel in the gas distribution plate120. The channel carries coolant to absorb the excess heat from theantennas 116 and surrounding components. A heat exchanger positionedoutside the chamber can be used to remove heat from the coolant.

Each monopole antenna 116 is partially surrounded by an insulatordielectric sheath 152. In particular, the sheath 152 can tightly coverat least the portion 116 c of the antenna 116 that extends into thechamber 110. The sheath can also cover the entire shaft 116 a, e.g., thewhole portion that extends through the gas distributor 120 and gasplenum 122 as well as the portion that extends into chamber 100 a. Thesheath 152 is transparent to the radiation generated by the monopole,e.g., the sheath 152 can be a microwave or RF transparent window sheath.

The sheath 152 can include a cylindrical section 152 a that surroundsthe shaft 116 a of the monopole antenna 116 and a floor 152 b thatcovers the bottom of the monopole antenna 116. The sheath 152 can alsoinclude an outwardly projecting flange or shoulder 152 c that extendsfrom the top of the cylindrical section 152. This flange or shoulder 152c separates the flange 116 b of the monopole antenna 116 from the topsurface of the showerhead 118. Conical monopole antennas 216 aresurrounded by a conical window sheath 252 (see FIG. 5).

The window sheath 152 can be formed of an electrically insulatingmaterial such as ceramic, aluminum oxide, or quartz. The sheath 152 canelectrically isolate the antennas 116 from the gas distribution plate120 and gas plenum plate 122 and can protect the conductor from theenvironment in the chamber 100 a. The sheath can also preventcontamination of the process, e.g., metal sputtering off the antenna116.

Referring to FIGS. 6 and 7, as noted above, the AC power source 110 canbe configured to supply power to different groups of monopole antennas116 at multiple different relative phases. To provide the differentgroups, the monopole antennas 116 can be phase-controlled individuallyor in groups. The power source 110 can include a single signal source306, the output of which is split and then subject to phase shifting,e.g., with analog circuitry. Alternatively, the power source 110 couldinclude multiple power sources, e.g., multiple digital signal generators306, that generate the multiple signals at the different phases.

In general, where the array 108 is divided into N groups, the AC powersupply can generate power at N different phases, e.g., N phasesseparated by 360/N degrees. The AC power supply can be configured togenerate AC power on a number of supply lines N at phases separated by360/N. The antennas 116 can be separated into a different amount ofgroups 308/408 such as 4, 5 or more groups. Each group of antennas canoccupy a spatially contiguous zone of the antenna array.

FIG. 6 illustrates an example of an array having groups that arearranged as linear rows. In particular, FIG. 6 illustrates an example ofa linear phased array. The array can split into N groups 308. The groupscan be provided by different rows 308 of antennas 116, e.g., each zonecan cover a generally linear stripe across the array. An N-number ofconductor lines 304 can be used to connect the power supply 110 to the Ngroups of antennas 116, providing a different phase to each group ofantennas. FIG. 6 illustrates the monopole antenna array 108 arranged ina hexagonal configuration, but this is not required.

FIG. 7 illustrates an example of an array having groups that areangularly spaced around a central axis. For example, each zone can covera circular sector; if the N zones are of equal sizes then the arc wouldbe 360/N degrees. In the illustrated example, the antennas 116 aredivided into six different groups 408. Each group 408 is coupled to adifferent conductor line 404, thus providing a different phase to eachgroup of antennas. The groups can be triangular zones of equal area onthe array.

Zones that are spatially adjacent to one another can be provided powerat sequentially adjacent phases from the multiple different phases. Forexample, in FIG. 7, there are six zones 410, and the signal applied totwo adjacent zones, e.g., zones 410-1 and 410-2, are separated by 60°.For example, power can be applied to the zones 410-1, 410-2, 410-3,410-4, 410-5 and 410-6 at relative phases of 0°, 60°, 120°, 180°, 240°,and 300°.

As another example, in FIG. 6, there are N zones 310, and the signalapplied to two adjacent zones 310-1 and 310-2 are separated by N/360°.For example, power can be applied to the zones 310-1, 310-2, . . . 310-Nat relative phases of 0°, (1/N)*360°, . . . (N−1/N)*360°. Although inthese examples the phases are separated by equal intervals, this is notrequired.

A polar phased array or a linear phased array to control the monopoleantennas 116 can be used with different configurations. For example, apolar phased array can use a six-phased power control configurationthrough a digital signal generator 406 in order to send a differentsignal to the groups of antennas 116 in increments of 60, as shown inFIG. 7. This increases the uniformity of the plasma similarly thanhaving a rotary antenna. In another example, as shown in FIG. 6, alinear phased array can be used in a n-phased power controlconfiguration using a digital signal generator 306. This allows forgreat controllability of antennas frequency and thus a more uniformplasma.

Phase shifting the power applied to different groups of antennas canincreases uniformity of the plasma deposition. In effect, this methodmimics a mechanically rotating rotary antenna during a plasma depositionprocess, albeit at extremely high rotation rates. The phase shiftingfrequency, i.e., the frequency at which a given zone returns to the samephase offset, can be set between 1-1000 Hz.

The implementation of FIG. 8 is similar to the implementation of FIG. 7,but includes an additional center antenna 420 positioned at the centerof the array 108 of monopole antennas 116. The center antenna 420 can belarger (e.g., greater diameter in the plane parallel to the array 108and support surface 106 a) than the other antennae 116. The centerantenna 420 can be driven with a one-phased signal, e.g., generated by adigital signal generator. An advantage of the center antenna 116 is toprovide power adjustment for the center-to-edge uniformity tuning in theprocess.

Alternatively or in addition to the phase shifting discussed above,power can be applied to the antennas in pulses. For example, power canbe applied in pulses at rate of 1-1000 Hz. The pulses can have a dutycycle of 5 to 95%, e.g., 25-75%. Within the given on-time of the dutycycle, power can be applied at RF or microwave frequencies, e.g., 300kHz to 30 GHz.

In some implementations, the plasma reactor can be used for thedeposition of a film in a PECVD process. In such a process, the layerbeing deposited can have some empty atomic lattice sites. As additionallayers are deposited, the additional layers cover the empty latticesites, thus forming voids in the crystalline structure of the depositedmaterial. Such voids are lattice defects and impair the quality of thedeposited material. A microwave source such as that employed in theembodiment of FIG. 1, generates a plasma with very low ion energy, sothat it does not disturb the lattice structure of the depositedmaterial, including the lattice defects. Such a microwave source mayhave a frequency of 2.45 GHz, which generates a plasma having anegligible ion energy level.

In general, the frequency of a microwave is not so accurate, and has afluctuation of approximately ±2%. Because the frequency of a microwavehas fluctuation, the reflectance of a microwave path changessignificantly, resulting in a change in the electric power of themicrowave supplied to the antennas and a change in plasma density. Inorder to control the plasma density according to the electric power of areflected wave, thus, it is necessary to accurately monitor thefrequency of a microwave, so as to compensate for the change in theelectric power of the reflected wave resulting from frequencyfluctuation.

While this document contains many specific implementation details, theseshould not be construed as limitations on the scope of any inventions orof what may be claimed, but rather as descriptions of features specificto particular embodiments of particular inventions. Certain featuresthat are described in this document in the context of separateembodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made.

Accordingly, other implementations are within the scope of the claims.

What is claimed is:
 1. A plasma reactor comprising: a chamber bodyhaving a floor, side walls and a ceiling defining an interior space thatprovides a plasma chamber, wherein the ceiling is provided by aconductive body that has a planar bottom surface facing inside theplasma chamber and has a plurality of apertures; a gas distribution portto deliver a processing gas to the plasma chamber; a workpiece supporthaving a support surface to hold a workpiece; an antenna arraycomprising a plurality of monopole antennas, each monopole antenna ofthe plurality of monopole antennae comprising an elongated rod extendingfrom above a top of the conductive body perpendicular to the planarbottom surface toward the workpiece support and through a respectiveaperture of the plurality of apertures in the conductive body, eachmonopole antenna of the plurality of monopole antennas comprising an endportion extending past the planar bottom surface and past a portion ofthe conductive body bounding the respective aperture through which themonopole antenna extends, and into the plasma chamber with a long axisof the elongated rod perpendicular to the support surface of theworkpiece support, wherein each monopole antenna of the plurality ofmonopole antennas is surrounded by an insulative sheath that extendsfrom the planar bottom surface to a tip of the monopole antenna to coverthe end portion including the tip of the monopole antenna, wherein atleast one of the plurality of monopole antennas comprise a tapered endportion extending into the plasma chamber; and an AC power source tosupply a first AC power to the plurality of monopole antennas.
 2. Theplasma reactor of claim 1, wherein the plurality of monopole antennasextend in parallel into the plasma chamber.
 3. The plasma reactor ofclaim 1, wherein the tapered end portion of the at least one of theplurality of monopole antennas that extend into the plasma chamber isconical.
 4. The plasma reactor of claim 1, wherein each monopole antennaof the plurality of monopole antennas comprises an outwardly extendingflange, the flange positioned on a far side of the conductive body fromthe plasma chamber.
 5. The plasma reactor of claim 1, wherein eachinsulative sheath of the plurality of insulative sheaths surrounds aportion of a monopole antenna of the plurality of monopole antennas thatextends through the aperture in the conductive body to insulate themonopole antenna from the conductive body.
 6. The plasma reactor ofclaim 5, wherein each monopole antenna of the plurality of monopoleantennas comprises an outwardly extending flange positioned on a farside of the conductive body from the plasma chamber, and each insulativesheath of the plurality of insulative sheaths comprises an outwardlyextending flange separating the flange of the monopole antenna from theconductive body.
 7. The plasma reactor of claim 1, wherein the pluralityof monopole antennas extend equal distances past the conductive bodyinto the plasma chamber.
 8. The plasma reactor of claim 1, wherein atleast some of the plurality of monopole antennas extend further into theplasma chamber than others of the plurality of monopole antennas.
 9. Theplasma reactor of claim 1, wherein the plurality of monopole antennasare spaced uniformly across the conductive body.
 10. The plasma reactorof claim 1, wherein each insulative sheath comprises a material selectedfrom ceramic and quartz.
 11. The plasma reactor of claim 1, wherein theworkpiece support is configured to hold the workpiece such that a frontsurface of the workpiece faces the plurality of monopole antennas. 12.The plasma reactor of claim 11, wherein the plurality of monopoleantennas extend in parallel into the plasma chamber.
 13. The plasmareactor of claim 11, wherein the plurality of monopole antennas face theworkpiece support without an intervening barrier.
 14. The plasma reactorof claim 1, wherein the plurality of monopole antennas are arranged in ahexagonal pattern.
 15. The plasma reactor of claim 1, wherein the ACpower source is configured to apply microwave power to the plurality ofmonopole antennas to generate plasma in the plasma chamber.
 16. Theplasma reactor of claim 1, wherein the plurality of monopole antennashave non-uniform sizes or shapes.
 17. A method of plasma processing aworkpiece, comprising: supporting a workpiece on a support surface in aplasma chamber; delivering a processing gas to the plasma chamberdefined by a floor, side walls and a ceiling, wherein the ceiling isprovided by a conductive body that has a planar bottom surface facinginside the plasma chamber and has a plurality of apertures; andgenerating a plasma in the plasma chamber by applying AC power to aplurality of monopole antennas, each monopole antenna of the pluralityof monopole antennas comprising an elongated rod extending from abovethe conductive body perpendicular to the planar bottom surface towardthe workpiece support and through a respective aperture of the pluralityof apertures in the conductive body, each monopole antenna of theplurality of monopole antennas comprising an end portion that projectspast the planar bottom surface and past a portion of the conductive bodybounding the respective aperture through which the monopole antennaextends, and into the plasma chamber with a long axis of the elongatedrod perpendicular to the support surface, wherein each monopole antennaof the plurality of monopole antennas is surrounded by an insulativesheath that extends from the planar bottom surface to a tip of themonopole antenna to cover the end portion including the tip of themonopole antenna, wherein at least one of the plurality of monopoleantennas comprise a tapered end portion extending into the plasmachamber.